Flame retardant compositions for use in electrical wire and cable products have traditionally required an oxygen index under ASTM D 2863 of at least 28 percent in order to pass a flame test promulgated by the Institute of Electrical and Electronics Engineers known as the IEEE-383 Cable Tray Flame Test established to determine the resistance of an electrical cable to propogation of flame along its length while laying in a vertical tray. In addition, it has been the general practice in the past to provide compositions for use as an insulation on electrical conductors with an oxygen index of at least 28 percent in order for the insulated conductor to pass a vertical flame test promulgated by Underwriters Laboratories known as UL VW-1. As a result, an oxygen index of at least 28 percent has been a criterion that most manufacturers follow in making compositions to be used as an insulation about an electrical conductor and as a jacket about an electrical cable with particular emphasis on the latter when the cable is destined to be laid in open trays from one location to another even though in most cases it is necessary to add high levels of flame retardants and fillers to the compositions to achieve an oxygen index of 28 percent or higher which may in itself cause a deterioration in other physical and electrical characteristics of the compositions and promote undesirable processing characteristics.
There exists then a need to be able to provide a flame retardant composition that is adapted preferably for use as an insulation about an electrical conductor and/or as a jacket about an electrical cable that has an oxygen index of less than 28 percent and is imparted with attractive physical and electrical properties while still being able to pass the UL VW-1 vertical flame test when in the form of an insulative covering about an electrical conductor and to pass the IEEE-383 Cable Tray Flame Test when in the form of a jacket about an electrical cable.